Calculation Of Additional Refrigerant Charge - Mitsubishi Electric CITY MULTI PUMY-P-VKM Series Installation Manual

3. Additional refrigerant charge
3.1. Calculation of additional refrigerant charge
Additional refrigerant charge
Refrigerant for the extended piping is not included in the outdoor unit when
the unit is shipped from the factory. Therefore, charge each refrigerant piping
system with additional refrigerant at the installation site. In addition, in order to
carry out service, enter the size and length of each liquid pipe and additional
refrigerant charge amounts in the spaces provided on the "Refrigerant amount"
plate on the outdoor unit.
* When the unit is stopped, charge the unit with the additional refrigerant through
the liquid stop valve after the pipe extensions and indoor unit have been
vacuumized.
When the unit is operating, add refrigerant to the gas check valve using a
safety charger. Do not add liquid refrigerant directly to the check valve.
Calculation of additional refrigerant charge
• Calculate the additional charge using the liquid pipe size and length of the
extended piping and total capacity of connected indoor units.
• Calculate the additional refrigerant charge using the procedure shown to the
right, and charge with the additional refrigerant.
• For amounts less than 0.1 kg, round up the calculated additional refrigerant
charge.
(For example, if the calculated charge is 6.01 kg, round up the charge to
6.1 kg.)
4. Refrigerant collecting (Pump down)
Perform the following procedures to collect the refrigerant when moving the
indoor unit or the outdoor unit.
1 Turn off the circuit breaker.
2 Connect the low pressure side of the gauge manifold to the service port of
the gas side stop valve.
3 Close the liquid stop valve.
4 Supply power (circuit breaker).
* Start-up of the indoor-outdoor communication takes about 3 minutes after
the power (circuit breaker) is turned on. Start the pump-down operation 3 to
4 minutes after the power (circuit breaker) is turned ON.
5 Confirm that SW3-2 is set to OFF, and then set SW3-1 to ON to perform the
test run for cooling operation. The compressor (outdoor unit) and ventilators
(indoor and outdoor units) start operating and test run for cooling operation
begins. Immediately after performing the test run for cooling operation, set
the outdoor service switch SW2-4 (pump down switch) from OFF to ON.
* Do not continue to operate for a long time with the switch SW2-4 set to ON.
Make sure to switch it to OFF after pump down is completed.
<Additional Charge>
Calculation of refrigerant charge
Pipe size Pipe size
Liquid pipe Liquid pipe
+
ø6.35 ø9.52
(m) × 19.0 (g/m) (m) × 50.0 (g/m)
Included refrigerant amount when shipped from the factory
Included refrigerant amount
4.8 kg
<Example>
Outdoor model : P125
Indoor 1 : P63 (7.1 kW)
2 : P40 (4.5 kW)
3 : P25 (2.8 kW)
4 : P20 (2.2 kW)
The total length of each liquid line is as follows:
ø9.52 : A + a = 30 + 15 = 45 m
ø6.35 : b + c + d = 10 + 10 + 20 = 40 m
The total capacity of connected indoor unit is as follows:
7.1 + 4.5 + 2.8 + 2.2 = 16.6
<Calculation example>
Additional refrigerant charge
19.0 50.0
40 × + 45 × + 3.0 = 6.1 kg (rounded up)
1000 1000
6 Fully close the gas stop valve when the pressure reading on the gauge
drops 0.05 - 0.00 MPa (approximately 0.5 - 0.0 kgf/cm
7 Stop the air conditioner operation (SW3-1: OFF). Set the outdoor service
switch SW2-4 from ON to OFF.
8 Turn off the power supply (circuit breaker).
* If too much refrigerant has been added to the air conditioner system, the
pressure may not drop to 0.05 MPa (0.5 kgf/cm
refrigerant collecting device to collect all of the refrigerant in the system,
and then recharge the system with the correct amount of refrigerant after
the indoor and outdoor units have been relocated.
Warning:
When pumping down the refrigerant, stop the compressor before discon-
necting the refrigerant pipes. The compressor may burst and cause injury
if any foreign substance, such as air, enters the system.
Total capacity of Amount for the
connected indoor units indoor units
+
~ 8.0 kW 1.5 kg
8.1 ~ 16.0 kW 2.5 kg
16.1 kW ~ 3.0 kg
A : ø9.52 30 m
a : ø9.52 15 m
At the conditions
b : ø6.35 10 m
below:
c : ø6.35 10 m
d : ø6.35 20 m
)
2
2 ). If this occurs, use a
3
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